While the apparatus and methods of this invention are useful in implanting ions into the surface of metals to produce surface alloying and may also be useful in other applications, the principal commercial use of ion implantation today is in the manufacture of large scale integrated circuit (LSIC) chips. Accordingly, for purposes of illustration but not of limitation, the methods and apparatus of this invention will be described in connection with the manufacture of LSIC chips. To understand the importance of the invention in the LSIC field, some background information on IC manufacture will be helpful.